1. Fumble luck

Recovering fumbles is random. There's no such thing as a team
that's consistently good at recovering fumbles over a large
sample size.

Right now, the Chiefs are getting incredibly lucky with fumbles.

They're recovering 56% of their own fumbles (the 12th-highest
percentage in the league), while recovering an eye-popping 73% of
their opponents' fumbles (the 3rd-highest percentage in the
league).

So they're recovering about two-thirds of all fumbles when the
should be recovering about half. It's pure luck, and there's no
rational reason for it to continue.

2. Turnover luck

Their average turnover margin per game is +1.7. That's first in
the league, and would tie for the largest turnover margin of the
last 10 years.

They've forced 23 turnovers, and returned six of those (26%) for
touchdowns. Against Buffalo on Sunday, Sean Smith returned an
interception for a touchdown when the Bills were on the one-yard
line and Tamba Hali returned a fumble for a touchdown. Without
those huge defensive plays, they don't win that game.

On their current pace, they'd score the most defensive touchdowns
of the last 10 years.

"A defense's tendency to force turnovers is fairly
important to the team's success, but it seems to be even more
unpredictable. In general, a team's ability to force fumbles
seems to be almost entirely luck. There is a little bit more
persistence in a team's ability to force interceptions, though it
isn't clear how much of this ability is just a residual effect of
general defensive ability."

3. Strength of schedule

This is obvious. Kansas City has faced the easiest schedule in
the league.

According to
Grantland's Bill Barnwell, Kansas City opponents have an
average Pythagorean win percentage of .392, the lowest number in
the league.

That's about to change. KC plays Denver twice, San Diego twice,
and Indianapolis in the last few months of the season.

4. Middling quarterback performance

Despite that easy schedule and the crazy, unsustainable rates at
which his defense is forcing turnovers, Alex Smith has been
exactly average.

He's 15th in the league in our
own quarterback rating system (which combines three advanced
stats). He doesn't take chances (30th in the league in yards per
attempt) and he's not particularly accurate (23rd in the league
in completion percentage).

In short, there is going to come a key game where Alex Smith
needs to single-handedly bring his team down the field and score
a touchdown late. There isn't a whole lot of evidence that he can
do that right now.